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The dementia timebomb

The brain of an Alzheimer's patient (left) shows significant signs of shrinking compared to a normal brain.

Dementia is a gradual decline of how the brain functions. It is incurable, and slowly interferes with a person's ability to carry out the normal tasks of daily living.

What is dementia?

Dementia is an umbrella term used to refer to a collection of symptoms that can result from a number of different diseases of the brain. There are many different types of dementia, but all tend to cause problems with memory, language skills, information processing, mental agility, understanding and judgement.

Dementia can also trigger other mental health problems such as personality changes, anxiety, mood swings and depression. In more advanced dementia, the person may lose the ability to get up and move, or the interest to eat or drink.

It is a progressive condition that gets worse over time and a person with dementia must increasingly rely on carers as it advances. There is currently no cure although there are treatments that can slow the progression of some types of the condition in some cases. Usually, only about one in three people show a positive response to such drugs.

There are around 100 different types of dementia. However Alzheimer's disease is the most common form, affecting 62% of those living with dementia. Many of these people will have a mixed pattern of dementia with the second most common type - vascular dementia - also contributing to their condition. This occurs due to the damage done to the small blood vessels in the brain.

The number of people with dementia is steadily increasing. While around 800,000 people have been diagnosed with the condition in the UK today, the Alzheimer's Society predicts this number will increase to one million by 2021 and 1.7 million by 2051.

Many others remain undiagnosed, especially in the early stages of dementia, so these figures may be much higher. This rise in numbers is attributed to advances in public health and medical care that enables people to live much longer than they used to. While one in 25 people aged 70 to 79 has a form of dementia, this rises to one in six people over the age of 80.

What causes dementia?

Dementia is caused by damage to brain cells, which stops them from communicating effectively with each other. Gradually brain cells die, leading to the shrinkage of the brain typically seen in brain scans in some types of dementia.

In neurodegenerative diseases, such as Alzheimer's, a gradual build-up of proteins inside and around brain cells can be seen. In Alzheimer's, these proteins form tangles, and sticky clumps known as plaques. It used to be thought that these were the cause of the brain dysfunction but more recent theories liken these plaques and tangles to the "ashes after the fire". In other words, they are the residual damage after the disease has swept through the brain.

Less common types of dementia

Dementia with Lewy Bodies sees tiny balls of protein develop inside nerve cells. This causes 10% of dementia cases in older people and is strongly linked with Parkinson's

Fronto-temporal dementia is caused by damage to the frontal lobe of the brain. It is relatively uncommon

Illnesses that may lead to dementia include Creutzfeldt-Jacob disease, multiple sclerosis and Parkinson's

Vascular dementia develops when the arteries supplying blood to the brain become blocked. This disrupts the supply of oxygen and nutrients to the cells, which leads to very small strokes resulting in brain damage.

Many people with dementia have a combination of Alzheimer's disease and vascular dementia.

Scientists are investigating the genetic background to dementia. It does appear that in a few rare cases the diseases that cause dementia can be inherited. Some people with a particular genetic make-up have a higher risk than others of developing dementia. Risk factors include age, smoking, heavy drinking, poor diet, and a lack of exercise.

Why haven't we found a cure?

One of the main obstacles to creating effective treatments to dementia is that scientists still don't fully understand it. The condition appears to result from a complex interaction of genes, lifestyle factors and other environmental influences. Without knowing the exact mechanisms that cause damage, especially in Alzheimer's, it's impossible to target the disease process effectively.

The blood-brain barrier is another problem. It keeps your brain healthy by preventing toxins reaching the brain. But it can also stop treatments getting through or working effectively. Drugs may only partly cross the barrier as they are too large or awkwardly shaped, which means that dangerous doses would be needed for them to work.

Even if drugs were found that could target the proteins causing damage to brain cells in neurodegenerative disease, the damage may already have been done.

Scientists found recently that dementia may start to develop decades before symptoms show.

Finally, dementia is very difficult to diagnose. There is no single test to pinpoint the disease. A diagnosis is made on the clinical judgement of a patient's symptoms, history and results from a variety of tests, many of which are used to rule out other possible causes.

There is also a stigma attached to the condition, as well as fear, that can make some health professionals reluctant to give the diagnosis. Some experts argue that with no effective treatments, early diagnosis has no benefits.

Less than half of those living with dementia in the UK have received a formal diagnosis. This causes problems for drug trials, as scientists can only guess what type of dementia patients have, and can only confirm their diagnosis at post-mortem.

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